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Biomedical subjects

E F Kharat'ian

Publications and source records attributed to E F Kharat'ian.

At least 19 recordsLinked to original sources
PubMed1995

[Stability of a new product of oxidative stress in bacterial cells].

Data on 32P-label incorporation with subsequent addition of non-radiolabelled o-phosphate suggest that the new phosphorus compound, 2-C-methyl-D-erythritol-2,4-cyclopyrophosphate (MEC), accumulated in the cells of some bacterial species in response to oxidative stress does not rapidly exchange phosphorus with external o-phosphate 3 hours after the introduction of its synthesis inducers into the Corynebacterium ammoniagenes culture. The accumulated MEC is retained in the cells despite the action of the cell wall synthesis inhibitor, chloramphenicol, or the energetic poisons, KCN and iodoacetate and also under anaerobic conditions. It has been shown that incubation of the cell-free lysate of a non-induced culture, Micrococcus luteus, with MEC does not result in MEC hydrolysis; therefore, MEC accumulation after the redox-mediator addition is hardly due to the hydrolase inactivation but, rather, is due to the activation of the MEC-synthesizing enzyme. The cells of C. ammoniagenes incorporate 32P from [32P]MEC but not 14C from [14C]MEC. This points to MEC hydrolysis prior to the uptake of its phosphoryl fragment by the cells. In this case 32P is found in the fractions differing by their position from MEC fractions. Experiments with sheep erythrocytes and mouse splenocytes revealed that MEC (10-100 micrograms per 1,000,000 splenocytes) does not influence the antibody production by these cells, whereas used at concentrations of 200-550 micrograms per 1,000,000 cells, MEC enhances the antibody production. However, while doing so, MEC causes the destruction of a considerable portion of splenocytes and sheep erythrocytes.

Animals↗
PubMed1983

[Structuro-functional properties of the bacteria Bacillus brevis in relation to the accumulation of gramicidin S in cells].

The culture of Bacillus brevis var. G-B R-form was grown in the presence of beta-phenyl-beta-alanine, the inhibitor of gramicidin S synthesis, is characterized by enhanced endogenous respiration and the DPI-reductase activity as compared to the culture synthezising antibiotic. The increased synthesis of the antibiotic in the region of the culture transition from the logarithmic growth phase to the linear one is associated with a decrease in the number of viable cells despite the fact that the culture on the whole does not die but continues to grow. The membranes prepared from young gramicidin S-free cells and from the cells enriched with the antibiotic possess identical electron micrograph images, IR spectra and protein sets as determined by polyacrylamide gel electrophoresis in a Na-DS system. However, in young cell membranes NADH and succinate dehydrogenase are insensitive to gramicidin S and only malate dehydrogenase is inhibited by this antibiotic. In aged cell membranes the activities of all mentioned dehydrogenases are suppressed. Malate dehydrogenase from young cells is weakly inhibited by thyrotrycin obtained from Bac. brevis ATCC 10068; succinate dehydrogenase is entirely insensitive to this antibiotic, while NADH-dehydrogenase is almost completely inhibited by it. The specificity of action on the respiratory chain of peptide antibiotics synthesized by the cells of one strain of Bac. brevis is suggestive of a possible regulatory role of these peptides in the metabolism of the producent. Hence the accumulation of gramicidin S which is adsorbed on the membrane and destroys the respiratory chain function to the cause of the low rate of oxygen uptake by the culture of Bac. brevis var. G-B R-form and of the low activities of DPI-reductases.

Alanine↗
PubMed1979

[Cytochrome b556 complexes solubilized from Micrococcus lysodeikticus membranes by triton X-100].

The integral protein of cytochrome b556 after its solubilization with Triton X-100 from M. lysodeikticus membranes was studied. The cytochrome was found in complexes differing in charge and size during preparative gel electrophoresis and centrifugation in a sucrose concentration gradient. Cytochrome b556, being in complexes, retains its ability to be reduced by NADH dehydrogenase. The electron micrographs of the membranes after solubilization by Triton X-100 demonstrated the maintenance of the membrane structure. It is concluded that native protein complexes marked with cytochrome b556 are extracted from the membranes under their solubilization.

Centrifugation, Density Gradient↗
PubMed1979

[Bacterial membrane proteins. Properties of Micrococcus lysodeikticus NADH dehydrogenase].

NADH dehydrogenase was isolated from M. lysodeikticus membranes with FAD as a prosthetic group. It was found the enzyme molecular weight is about 140000 in 0,01 M phosphate buffer, pH 7,4 in 1% Triton X-100. The enzyme molecules are dimers consisting of two subunits with molecular weight of 70000. The content of alpha-helical regions is 30%, that of beta-forms is 13%. The protein globule is cross-linked with the disulfide bonds and has hydrophobic regions on its surface.

Cell Membrane↗
PubMed1979

[Study of membrane proteins from Microccus lysodeikticus using immunochemical methods].

Using immunoelectrophoresis, the antigenicity of various protein fractions of the Micrococcus lysodeikticus membranes was evaluated. It was shown that both the peripheral and integral membrane proteins possess the antigenic determinants. The antiserum exhausted by the M. lysodeikticus mebranes loses its ability to interact with intergral proteins, which are not solubilized by Triton X-100. It was thus assumed that the integral proteins are exposed on the membrane surface constantly or periodically and that there exist no proteins which are completely and permanently incorporated into the lipid bilayer. The respiratory chain of the M. lysodeikticus membrane is inhibited by membrane immunoglobulins by 50%. This is probably due to the presence in the membrane antiserum of antibodies specific to the respiratory chain enzymes. Evidence for this assumption can be derived from the fact that partially purified cytochrome b556 forms a precipitation zone with the membrane antiserum and that the activity of membrane NADH-dehydrogenase is inhibited by a monoserum against NADH-dehydrogenase.

Cell Membrane↗
PubMed1976

[Ultrastructure of L forms. Report 5. localization of dehydrogenase activity in L form cells].

A study was made of deposition of diformazan TNBT and TCNBT in the presence of succinate and without it in stable L-forms of Str. pyogenes group A, St. aureus and L. monocytogenes. Diformazan proved to deposit on the cytoplasmic membrane, in the lamellar mesosomes and myelin-like structures and also on individual intracellulor membranes not forming special membrane organoids. Diformazan was localized on the membranes mostly asymmetrically, on the cytoplasmic membrane-on its internal side, and on the ring-like intracellulor membranes- externally. Localization of diformazan on the ring-like membranes is atributed to the fact that ring-like membranous structures in the L-forms formed as a result of invagination of the cytoplasmic membrane in the same way as bacterial mesosomes. Since L-form cells could not be released of endogenous substrates by the methods elaborated for bacteria, cytological data did not permit to ascertain dehydrogenases, responsible for asymmetrical localization of diformazan on the L-form membranes. On the basis of these data one can judge only the sum total activity of dehydrogenases in different membranes.

Formazans↗
PubMedDate not supplied

[Composition and properties of the outer cell wall layer in Bacillus brevis--the producer of gramicidin S].

Two membrane antigens were found by cross immunoelectrophoresis in the cell walls of Bacillus brevis var. G.-B., R form, which started to synthesize gramicidin S (20 mg per 1 ml of cultural broth). The cell wall contained no membrane components in cells at the beginning of the logarithmic growth phase. The protein with a molecular mass of 100 kDa is a component of the cell wall outer layer. The protein is not digested by trypsin or pronase when it comprises the cell walls of cells synthesizing gramicidin S. In the preparation of isolated cell walls, this protein becomes susceptible to the action of the above proteases only when the peptidoglycan layer is broken down by lysozyme. Electron microscopy of cells treated with proteases and shadowed with a metal revealed that many cells lacked the cytoplasm. Therefore, the outer layer of B. brevis R cell wall contains small regions susceptible to the action of protease along with regions composed of the 100 kDa protein and resistant to these enzymes. It is possible that the small regions contain membrane components.

Antigens, Bacterial↗
PubMedDate not supplied

[The cell wall of Bacillus brevis producing gramicidin S, a cyclodecapeptide antibiotic].

Gramicidin S is tritiated in Bacillus brevis G.-B. intact cells by activated tritium atoms (which is indicative of its surface localisation). The cell wall protein is tritiated very weakly, which shows that it is screened, apparently, by gramicidin adsorbed on its surface. The cell wall protein is not a glycoprotein and its interaction with exogenous gramicidin S causes cell aggregation. As follows from the Rf value after the chromatographic separation of B. brevis lipids, the reaction of staining, and the data of H-NMR spectroscopy for the fraction of phospholipids, the main membrane phospholipid is an anionic acetylated phosphatidyl ethanolamine.

Bacillus↗
PubMedDate not supplied

[Membrane potential in Escherichia coli bacteria subjected to the action of low temperature freezing and blood serum complement].

The action of a blood serum complement on Escherichia coli cells or their freezing does not cause cell destruction visible in the electron microscope, but the permeability barrier is disordered and exogenous substrates can penetrate into the cell. When these exogenous respiration substrates are oxidised, the energy-dependent uptake of phenyl dicarboundecarborane (PCB-), a lipophilic anion and an indicator of the membrane potential, is observed. Apparently, the uptake of PCB- is associated with the generation of local membrane potentials when the permeability barrier of cells is damaged.

Complement System Proteins↗
PubMedDate not supplied

[Action of benzohydrothiochromylium salts on bacterial membranes].

Cultivation of Staphylococcus 209-P and Micrococcus lysodeikticus cells on media containing new antibacterial preparations--iodide and trifluoroacetate derivatives of benzohydrothiochromylium resulted in a remarkable lesion of the membrane respiratory apparatus, i.e. the amounts of membrane polypeptides, the specific concentration of cytochromes, the activities of reductases and oxidases--NADH, malate and lactate decreased. Profound changes in the cell cytology were observed.

Anti-Bacterial Agents↗